220 in / 205 out? I'd expect a much larger delta than 15F. Same for idle (190 - 172 = 18F). Somehow that radiator isn't doing the job. You can feel air rushing through it, right?
Can you pop the cap and see the fins inside the radiator? If you can't get a peak maybe you can shoot a photo with your cell phone then look at that. Don't forget the flash (and say 'cheese').
You can also pull the lower hose and run a garden hose through it. That will tell you if it's flowing but that doesn't mean the inside isn't covered in scale acting as an insulator.
Just some thoughts . . . .
Good luck!
- c bob
